How to store a list of objects in sqflite?

user_7120574 0
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I want to use the sqflite package to store my objects. I read some articles, tutorials and examples about it. So far I understand everything. But none of them covers my use case:

I have a class named Foo. This class holds beside some primitive fields an object of the class Bar. Bar has only primitive fields. Additionally Foo has a list of objects of the type Baz. Baz has also only primitive fields.

class Foo {
  // simple fields

  String id;

  Bar bar;
  List<Baz> bazs;
}

class Bar {
  // only primitive fields
  
  String id;
}

class Baz {
  // only primitive fields

  String id;
}

I want to connect the bar object with the foo object in the database and the same with the bazs objects. How do I do it? Whats the best way?

I'm not really experienced wit SQL. I know what SELECT, WHERE, ORDERBY and so on means but my knowledge does not get much further.

I found this qustion in Stack Overflow but I wonder if it is actually efficient to store all the values as a JSON. What happens if the JSON gets really big?

Currently my only idea is to store the id of the bar object as a field in the foo object or vica versa. foo could also hold a list of the ids of the bazs objects. Or each baz objects holds the id of the foo object. Is this a good solution?

Is there a possibility to let sqflite handle the relations between the objects?

sqflite dart flutter persistence sqlite
1 Answers

You need to create 3 tables:

  1. Foos: [fields]:
  • id
  1. Bars: [fields]:
  • foo_id: a foreign key that points to the id field of Foo
  • bar_id: which is the bar's id
  1. Bazs: [fields]:
  • foo_id: a foreign key that points to the id field of Foo
  • baz_id: which is the baz's id

Now lets say that you want fetch a Foo record with and Id = 3 along with the bar and bazs

  1. fetch the foo record:
SELECT * FROM foo WHERE id = 3;
  1. fetch bar where foo_id = 3
SELECT bar_id
FROM bars
INNER JOIN Foo on B.id = bars.foo_id;
  1. fetch bazs where foo_id = 3
SELECT baz_id
FROM bazs
INNER JOIN Foo on B.id = bazs.foo_id;

It would be easier if you use moor package to implement a sqllite DB

user_118341980
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